Random people reinforcing the protagonist(s) or the opponents for the final battle, for no apparent reason other than to increase the magnitude of the fight. A less predictable version of The Cavalry
or just about any Deus ex Machina
If all the people are called rather than showing up for no reason, it becomes Gondor Calls for Aid
Anime and Manga
- The Whitebeard War was heading this way in One Piece. Every single Marine who ever appeared in the comic was there, plus a ton more. A bunch of New World pirate captains. The surviving male members of Baroque Works. Buggy the Clown. A small army of escaped prisoners and transvestites. Blackbeard and crew. However, it wasn't until Shanks and Trafalgar Law showed up that this really proved to be the case.
- The end of the second season of Vandread featured lots of people coming to Nirvana's aid against the Earthling(s). Although this wasn't really expected, it has been justified by all of them coming from planets where Nirvana's crew did something good or otherwise impressed the locals over the course of the two seasons.
- Indirect version in Tengen Toppa Gurren Lagann. During the final battle with the Antispiral, after a wormhole or something opens up to Earth, every single human being on Earth is seen believing in Team Dai-Gurren to take down the Antispiral. Remember, Spiral Power comes from belief and determination, both of which the entire population is supplying Simon and co. with.
- The last scene in Monty Python and the Holy Grail, in which King Arthur's small band of knights suddenly becomes a huge army.
- Subverted in The Matrix Revolutions, wherein the 9 BILLION copies Agent Smith made of himself just stand around and watch Smith 1.0 and Neo fight.
- In Casino Royale (1967), everyone from the British army to Cowboys and Indians show up for the last battle. There is no reason for this. (Nor, really, anything else in the film).
- Similarly, the brawl at the end of Blazing Saddles is between all the bad guys and all the townsfolk and spills out into adjacent studios. A baker shows up in the studio commissary and hands out custard pies to the brawlers "for the big pie fight", even though he'd had no idea of knowing there was going to be a fight of any kind.
- The Blues Brothers, Inverted. While the police have been chasing Jake and Elwood for the whole film, at the climax, hundreds of police men, SWAT team, soldiers, tanks, and helicopters show up out of nowhere in downtown Chicago to apprehend two unarmed men.
- Harry Potter and the Deathly Hallows - everybody and their dog shows up for the Battle of Hogwarts.
- Possibly overlaps into Gondor Calls for Aid, since a lot of the people who showed up were called upon to be reinforcements.
- Diana Wynne Jones actually does this a lot in many of her books; Howl's Moving Castle is probably the best known.
- The Battle of Five Armies in The Hobbit. First, the dwarves and the men are about to start a battle. Then the wood elves show up with their own claims/demands (but these are largely compatible with those of the men, so it's still essentially 13 dwarves vs. men and elves). Then Thorin's cousin Dáin from the Iron Hills arrives with a proper dwarf army at his back. After a very small amount of that they all at least temporarily put aside their differences to fight the goblins. The eagles appeared later and started doing a Death from Above thing on the goblins.
- In Final Fantasy IV, the entire inactive party prays to revive the entire felled party at the end of the game, just prior to fighting the surprise final boss. And each member appears to say a line to the party in the process, to boot.
- Even dead party members show up to offer words of encouragement.
- Earthbound while fighting the Big Bad, the only way to beat him is to use the up until then useless skill "Pray," which causes all the NPCs in the world, plus the player, to pray together, which destroys the Big Bad.
- The citizens of Station Square did this in Sonic Adventure. Though how they were cheering, let alone alive, after the city had been destroyed is beyond anyone.
- Played literally in Castle Crashers where after you defeat the final boss, you and the princess ride on the crystal back to your castle. The final scene in the game before your princess turns out to be a clown, comes back to the party from the first scene only now filled with just about every character in the game, all having fun and drinking.
- Never Winter Nights 2: Mask of the Betrayer has the final confrontation taking place in your own mind as it is being devoured by the Spirit-Eater curse, as you fight you call your allies and friends (some of which are dead) to assist you.
- Similarly, Jade Empire won't let your party members join you in the final showdown, but they (those who remained loyal anyway) will help you take out the Big Bad 's minions.
- In the PC fantasy kingdom sim Majesty, you (as the sovereign) are not allowed to have certain groups, usually of warring religious factions, in your kingdom at the same time. However, in the final quest, as your kingdom's map gets filled out by exploring parties, they stumble across hidden pockets of every conceivable group of adventurers — all of whom promptly join in aiding you in the final battles against every villain you've encountered up to this point in the game. All the heroes versus all the villains, including the ones they already killed.
- At one point in Disgaea 3 a show of support from Mao's friends goes overboard into silly when every minor opponent up to that point shows up to lend their support.
- When you're facing down Feinne the World Eater in Soul Nomad & the World Eaters for the second time, after she's annihilated the town everyone laments how you cannot hope to defeat her power. Cue textbook Big Damn Heroes moment as the knights of Raide and Christophe's mercenaries show up to lend their aid.
- Chapter 10 of Red vs. Blue: Revelation has just about every main character from the Red and Blue teams who had been split from the party return for an epic confrontation with yet another returning character, Tex.
- And she then proceeds to lay an utter asskicking against every one of them.